What caused communism to fall in the Soviet Union?

There has been loooong time ago I wrote the last comment but still people keep writing threads about fall of USSR or communism.What is communism, I dunno. Marxists say themselves practice is the criteria for the truth. What is the practice in USSR?- Economy, bad or good? What is the practice? As it collapsed, we can say, it was bad - one reason of fall of USSR- Violence in general. No institution (as well as states) is sustainable, which created on basis of violence. How was created the USSR? By Red Army during 1917 - 1947 - these are the years USSR was established within the borders we know (knew). What was the so-called October Revolution - as we know (more or less by now) - it was just coups d'état of limited group of (para)military forces used the weakness of the society. After what the Red Army was established - what Red Army did in the area of pre-2-nd WW USSR? Violently conquered all the states/countries/areas of former Russian empire (Ukraine, Caucasus, Central-East, Far-East etc - only Finland, Baltic states and Poland "failed") - probably everyone has seen the maps of formation USSR in 1920 which period was named as Civil War. In the beginning of 2-nd WW the Baltic states were conquered again. - and this time sucessfully for 50 years. Actually there was any state-institutions established voluntarily - all institutions were established under the control of Lenin's "comrades" - officially it was named "Proletarian Dictatorship".What is the practice? As soon as the military grip (Red Army, KGB etc etc) was loosened, all the nations get free. Which means - what was established by violence, is not sustainable without it.Violence, eg the lack of violence (weak leadership of KGB or army) is the main reason of fall of USSR and communism!If USSR was an example of communism, then what the practice says...?

Considering that Hoxha died in 1985, and that he held dogmatic and silly views on Soviet society (e.g. Stalin was infallible, the USSR somehow became a capitalist country because aspects of Stalin's leadership were criticized as departing from Leninism, Soviet foreign policy was "social-imperialist," etc.), I don't see how that'd be particularly helpful.